Cooler

ABSTRACT

A cooler, having individual cooling elements (1) of stacked construction having ducts (25) extending in parallel to one another, each of which delimits a flow chamber (29) for the throughflow of a liquid medium to be cooled, between which at least two layers (3, 5) of individual rows of meandering fins (34) extend, which for the throughflow of air jointly delimit a further flow chamber (26, 28) each, is characterized in that the respective one flow chamber (29), free of obstacles, permits a laminar flow of the liquid medium through the assignable duct (25) in one throughflow direction, in that the height (H1) of each fin (34), viewed transversely to the direction of throughflow of the liquid medium, has at least the same height as the free throughflow cross section of the flow chamber (29) of the adjacently arranged duct (25), viewed in parallel to the extension of the respective fin (34), and in that in every layer (3, 5), a plurality of rows (36) of several fins (34) are arranged in succession, which each viewed in the direction of throughflow of the duct (25) are offset from each other.

The invention relates to a cooler, having individual cooling elements ofstacked construction having ducts extending in parallel to one another,each of which delimits a flow chamber for the throughflow of a liquidmedium to be cooled, between which at least two layers of individualrows of meandering fins extend, which for the flow of air jointlydelimit a further flow chamber each.

Coolers of this type, which operate as liquid-air heat exchangers, arestate of the art, see for instance DE 10 2014 001 703 A1. To achieve thecooling capacities required for the individual applications, air-liquidcoolers are usually operated as active coolers having cooling fans thatgenerate the air flow required for an effective heat exchange in theflow chambers. To avoid the setup and energy costs associated with theuse of fans, it is known, see DE 10 2011 107 013 A1, in coolers,intended for the dissipation of the heat to the environment, to utilizethe wind flow flowing around the nacelle or tower of wind turbines forthe generation of the cooling air. As shown in said document, in aneffort to achieve a sufficiently high flow velocity in the flowchambers, the respective heat exchanger is located on the wind turbineat a point where the air flow is accelerated by the displacement effectresulting from the geometry of the wind turbine.

This solution is suboptimal in that the constraint of arranging the heatexchanger in a specific place interferes with the free design of thegeometry of the nacelle and/or tower. Also, there is room forimprovement in the effectiveness of heat exchange despite the specialposition arrangement of the cooler, so that an additional fan may berequired as an active flow booster.

DE 21 63 951 B2 describes a generic heat exchanger having a perturber,arranged in the interior of a tube through which fluid flows, whereinsaid perturber consists of a thin metal strip having projecting lugsarranged in rows and bent from openings, the bent ends of said lugs restagainst the inner wall of the tube, wherein the lugs are provided withone window each, and wherein transversely arranged recesses areadditionally provided in the metal strip between the openings. This isto cause increased vorticity of the fluid medium and consequentlysafeguard a good heat transfer. However, because of the introducedinhibition by means of the mentioned perturber, pressure losses occur inany case, even if they are described as small, and there is a longerresidence time of the fluid to be cooled in the heat exchanger, whichreduces the throughput of fluid to be cooled and degrades the overallenergy balance of the heat exchanger.

From WO 03/076860 A1 a further cooler in the form of a heat exchanger isknown, in particular for motor vehicles, having flat tubes through whicha first fluid can flow internally, to which flat tubes a second fluidcan be applied externally, wherein said flat tubes are arrangedessentially transversely to the direction of flow of the second fluidand in parallel to one another and are spaced apart from one another,thereby forming flow paths for the second fluid passing through the heatexchanger, wherein cooling fins are arranged in the flow paths, eachextending between adjacent flat tubes, wherein a plurality of corrugatedfins are provided as cooling fins, which are arranged in succession inthe flow direction of the second fluid and are laterally offset withrespect to one another. The flat tubes are provided with flow guideelements for flow guidance and their ends are connected to manifolds orcollector pipes in a fluid-conveying manner. The corrugated fins eachform individual fins, forming only one layer of a row of meanderingfins, which are arranged in succession and offset from one another,viewed transversely to the direction of flow through the flat tubes, andwherein said fins have gill-like slots in the fin walls for improvedheat transfer of the second fluid to be conveyed, which also contributesto increasing the stability of the heat exchanger.

Based on this prior art, the invention addresses the problem ofproviding a cooler of the genus mentioned at the outset, which has ahigh efficiency, is inherently stable and is inexpensive to implement.

According to the invention, this problem is solved by a cooler havingthe features of claim 1 in its entirety.

Because, according to the characterizing part of claim 1, the respectiveone flow chamber, free from obstacles, permits a laminar flow of theliquid medium through the assignable duct in one throughflow direction,a high throughput of liquid medium to be cooled is achieved, resultingin an energetically favorable operation having a high cooling capacity.

In that, furthermore, the height of every fin, viewed transversely tothe direction of throughflow of the liquid medium, has at least the sameheight as the free throughflow cross-section of the flow chamber of theadjacently arranged duct, viewed in parallel to the extension of therespective fin, and in that in every layer a plurality of rows ofseveral fins arranged in succession, which each viewed in the directionof throughflow of the duct are offset from each other, a very high airthroughput compared to single-layer systems is achieved because of thestacked layers, arranged directly on top of each other, of therespective cooling element, resulting in a high efficiency, such thatthe cooler according to the invention can be used as a passive heatexchanger utilizing the surrounding air flow with particular advantagein wind turbines, for instance according to DE 10 2012 017 462 A1,according to the feature configuration of patent claim 13. Withoutweakening the wall by adding cooling guide elements, such as gill-likeslots, this results in a trouble-free flow guidance at a high-level heatexchange, which can also be implemented in a particularly inherentlystable and cost-effective manner.

The fins, against which air flows, of successive tiers of stacked flowchambers are each in thermal contact with an assigned cooling mediumduct. This allows for a substantially increased heat dissipation fromthe liquid medium to be cooled, so that the cooler according to theinvention is characterized by a high cooling capacity even at limitedflow velocities of the cooling air and can be used with particularadvantage and at a mounting area, that can be freely selected, on windturbines. Fins having a correspondingly high bar height permit a highthroughput of cooling air at correspondingly high-level heat transferrates between the fins of the cooler and the cooling air.

In a preferred exemplary embodiment, it is provided that at least partof the fins of every layer adjoining each other extends in a bar-likemanner each, forming a waveform between two respective oppositedeflection points, and that deflection points of two adjacent layers arecongruently facing each other in a joint plane adjoining the adjacentlyarranged ducts of a cooling element.

Fin components that are congruent with each other, viewed in a verticalplane for an upright cooler, permit a simplified manufacture becausesheet metal parts having the same shape can always be used for theoverall cooler. The material may be a sheet material, preferably made ofan aluminum material having good thermal conductivity. In anadvantageous embodiment of the cooler according to the invention, it isprovided that in the respective plane a partition wall extends inparallel to the flow direction of the liquid medium in the ducts. Thepartition walls, each arranged horizontally when the cooler is inoperation, increase the stability of the layers of fins within theoverall arrangement and at the same time augment the heat transfer.

Advantageously, the respective partition wall has the same materialthickness as the fins forming the waveform. The use of uniform sheetwall thicknesses simplifies production and reduces costs.

Advantageously, the bar height of a single bar-like fin is preferablythree to six times, and particularly preferably five times, the heightof the flow chamber for a duct conveying the liquid to be cooled. Amultiple of the bar height also means obtaining a multiple of theair-cooled surface of the fins in relation to the volume of the mediumto be cooled in the respective medium-conveying duct. In this way, ahigh throughput of cooling air and a large heat transfer per individualcooling element are achieved, wherein said individual cooling elementsmake up the cooler in stacked construction. In this respect, an optimumof the quantity ratio between the medium to be cooled and the coolingmedium (air) is achieved.

Advantageously, the flow chamber of every duct has a free openingcross-section, which is exclusively rectangularly delimited byperipheral duct walls whose material thickness preferably matches thewall thickness of the respective fin.

It is also advantageous to select the offset in such a way that therespective fin of a further row of fins arranged between two to eachother parallel, offset-free rows of fins extends offset from theadjacent fins of the two adjacent rows of fins by a predeterminableaxial distance, in parallel to the respective duct, viewed in its flowdirection. The offset creates a kind of air divider for the cooling airhaving improved, homogenized flow guidance, resulting in a particularlyeffective heat transfer. The offset of the fins can also be seen infront view on the cooler, in which the offset row projects or is offsetback by the aforementioned axial spacing in relation to the adjacentrows, as viewed in the direction of the fluid flow.

Advantageously, the arrangement can be such that the offset is 3 mm to 8mm, preferably 4 mm to 6 mm, particularly preferably between 5 mm to 5.9mm. Preferably, for fins having a greater height or length between theadjacent respective ducts, the offset should also have higher values.

In advantageous exemplary embodiments, the height of a single fin,viewed transversely to the direction of flow through a duct, is between5 mm to 15 mm, preferably 12 mm, wherein the total depth of the coolerhaving a plurality of rows of fins arranged in succession in ahorizontal plane is 60 mm to 90 mm, preferably 63 mm to 82 mm, in depth.

In particularly preferred exemplary embodiments, the thickness or wallthickness of the fins, formed from a sheet material, is 0.15 mm to 0.4mm, preferably 0.2 mm, and the thickness of a panel, consisting of sheetmaterial, as a partition wall between the rows of fins is 0.2 mm to 0.8mm, preferably 0.4 mm. It is advantageous to use aluminum as the sheetmaterial for both the fins and the respective duct.

In particularly advantageous exemplary embodiments, the meander shape ofthe respective fin row has fins, extending in parallel to one another,and two adjacent fins of the fin rows are each integrally interconnectedby the deflection points and the connecting bars, respectively, whichextend in parallel to the ducts having boundary walls in their directionof flow. Because of the parallel orientation of the connecting bars onthe deflection points, they are in full contact with the boundary wallsof the ducts, so that extensive contact surfaces are formed forconducting heat from the fins to the relevant duct. These deflectionpoints of the meandering fins compensate thermal stresses occurringduring operation because of thermally induced expansion.

In a preferred embodiment of the cooler, the rows of fins and the ductsextend between two media-conveying main struts forming the fluidconnections with the ducts and span a rectangular front face as thecooler surface, wherein 20 to 48, preferably 25 to 63, particularlypreferably 54 ducts form the effective cooler surface. The large numberof ducts permits a favorable ratio of duct surface area to the volume ofthe medium to be cooled and a particularly effective cooling, inparticular in conjunction with the remaining geometric design of thecooler.

A further subject matter of the invention according to the patent claim13 is a wind turbine, in which at least one cooler according to one ofthe patent claims 1 to 12 is spatially assigned to a nacelle of theturbine for the purpose of flow through the flow chambers without anyfan drive only based on the blade air flow and/or purely wind-drivenambient air. The cooler according to the invention enables asubstantially increased heat dissipation from the liquid medium to becooled, such that it is characterized by a high cooling capacity, evenfor limited flow velocities of the cooling air, and can thus be usedwith particular advantage and at a mounting area, that can be freelyselected, on wind turbines.

The invention is explained in detail below, with reference to anexemplary embodiment shown in the drawing. In the Figures:

FIG. 1 shows a highly schematically simplified and cut off perspectiveoblique view of the end region, adjacent to the nacelle, of a windturbine provided with two coolers according to the invention;

FIG. 2 shows a perspective oblique view of the exemplary embodiment ofthe cooler according to the invention;

FIGS. 3 and 4 show a front view and a top view, respectively, of theexemplary embodiment of the cooler;

FIG. 5 shows an illustration, drawn at approximately twice themagnification of a practical embodiment, of the partial area, designatedby V in FIG. 3, of the exemplary embodiment;

FIG. 6 shows a front view of a section of two rows of fins succeedingeach other in the direction of air flow;

FIGS. 7 and 8 show perspective oblique view and top view, respectively,of three rows of fins succeeding each other in the direction of airflow; and

FIG. 9 shows a perspective front view on a part of a duct, not connectedto a main strut, for the medium to be cooled, wherein the wallthicknesses are shown larger for better illustration.

FIG. 1 shows only the nacelle 4 of a wind turbine 2 in a highlysimplified form, wherein said nacelle 4 is rotatably arranged on a tower6 only suggestively shown. Only a hub 10 together with blade roots 12 ofrotor blades, otherwise not shown, of a rotor, located at the front 8 ofnacelle 4, are shown. Two coolers 18, according to the exemplaryembodiment of the invention, are arranged adjacent to each other on theupper side 14 of the nacelle 4 in such a way that their front faces 16are exposed in the direction of the wind flow flowing along the nacellesurface 14. Further details of the cooler 18 can be taken from FIGS. 2to 9.

As shown in FIGS. 2 and 3, the front face 16, exposed to the wind flow,of the cooler 18 is square in outline. On both sides, main struts 20,forming a support structure, adjoin the front face 16, wherein each ofsaid main struts 20 is shaped like a bar-like hollow box having anarbitrarily shaped cross-section, which in the exemplary embodimentshown is square, and each main strut 20 forms a collecting chamber forthe liquid medium to be cooled. This can be a water-glycol mixture thatis heated by the lost heat generated in the operation of the windturbine, wherein said lost heat is to be dissipated to the ambient air.Ports 22 for the inflow and outflow of the medium are arranged on thestruts 20, which form a medium passage to the interior of the respectivecollecting chamber. While FIGS. 2 to 4 show the ports at the upper endsof the struts 20, it goes without saying that the ports 22 areconveniently provided on the underside, facing the nacelle top 14, ifthe coolers 18 are attached to the top 14 of the nacelle 4.

In the exemplary embodiment shown in the drawing, the lateral length ofthe square outline and thus the depth of the radiator measuredperpendicular to the plane of the end face 16 is 63 mm. The height ofthe struts 20 measured in the drawing plane of FIG. 3 and the spacing ofthe struts 20 are such that the front faces 16 span a rectangular frontface 16, exposed to the ambient wind, as a cooler surface. Boundarywalls 24 extend between the struts 20, only part of which boundary wallsare numbered in FIGS. 2 and 3 and which are formed from thin,flat-surfaced aluminum plates, whose width matches the lateral length ofthe square outline of the struts 20, see FIG. 4. The boundary walls 24are, see FIGS. 5 and 9, each combined into groups of two, in which thewalls 24 extend equidistantly from each other and in parallel and, witha front wall 23 and a rear wall 23′ in between them, form a duct 25 forthe medium to be cooled, in particular in the form of a liquid. Thegroups of two of the boundary walls 24, extending equidistantly fromeach other and in parallel, each delimit between them a combination oftwo flow chambers 26 and 28, separated by a further panel used as apartition wall (27), wherein through said flow chambers 26 and 28 theambient air can flow from the front face 16 forming the cooling surface.The ends of the ducts 25, formed between the boundary walls 24, are eachconnected to the collecting chamber inside the struts 20 in a fluidconveying manner and, in operation, the liquid medium to be cooled flowstherethrough. In this example, the width of the ducts 25, measuredtransversely to the longitudinal direction of the duct, is 3 mm each.

The cooler 18 shown in the figures is formed of individual coolingelements 1 in a stacked structure with the ducts 25 extending inparallel to each other. In any case, any single cooling element 1 has acombination of two layers 3, 5 of meandering fins 34, wherein the twolayers 3, 5 of a cooling element 1 are separated by the partition wall27, which extends in a horizontal plane E.

As shown in particular in FIG. 9, each individual duct 25 ofrectangular, in particular square, cross-section is delimited by thewalls 24 at the top and at the bottom and by a front wall 23 and a rearwall 23′. In this respect, the duct 25 mentioned spans a kind of flowchamber 29, which, kept free of obstacles, permits a laminar flow of theliquid medium to be cooled through the duct 25 in a flow direction.

The vertical height H1 of every fin 34, viewed transversely to the flowdirection of the liquid medium, has at least the same height H2 as thefree flow cross-section of the flow chamber 29 of the adjacentlyarranged duct 25, viewed in parallel to the extension of the respectivefin 34 in its heightwise orientation. In every layer 3, 5, there is inturn a plurality of rows 36 of a plurality of fins 34, which arearranged in succession in the horizontal direction (see FIGS. 7 and 8),and each has an offset P (see FIG. 6) from one another, viewed in thedirection of flow through the duct 25. This axial offset P of the rows36 arranged in succession is viewed in the horizontal direction towardsthe front face of the cooler 18.

As can be taken from FIGS. 5 to 9, for transferring the heat of theliquid medium flowing through the ducts 25 to the air flowing throughthe flow chambers 26 and 28 fins 34, whose surfaces are flowed againstby the cooling air flowing therethrough, are located in the flowchambers 26, 28. As is most clearly shown in FIGS. 7 and 8, the fins 34,which are only partially numbered in the figures, are arranged in thefin rows 36, wherein the rows 36 extend in a direction in parallel tothe plane of the front face 16 and the rows 36 are arranged insuccession viewed in the direction of flow. The identically formed fins34 are each formed by sheet metal parts made of aluminum sheet having arectangular outline, wherein the sheet thickness in this exemplaryembodiment is 0.2 mm. The fins 34 extend in a direction in parallel tothe direction of the air flow and perpendicular to the longitudinaldirection of the ducts 25 and have a height H1, which matches the heightof the assigned flow chamber 26 or 28. In this example, the height ofthe flow chambers 26 and 28 and accordingly the height H1 of the fins 34is 10.3 mm. At the ends adjacent to the boundary walls 24, the fins 34are interconnected by connecting bars (also not all numbered in thefigures), forming deflection points 38 and continuing in one piece thesheet material, wherein the connecting bars lie against the facingboundary wall 24 in a planar manner and are secured thereto by bondingor welding. Owing to the planar contact of the deflection points 38,every fin 34 is in close heat-conducting contact with a duct 25. Thisalso applies to the articulation of the fins 34 to the panel spanning apartition wall 27, wherein said panel extends in the horizontaldirection.

As shown in FIGS. 7 and 8, the rows 36 of fins 34 with the flow chambers26 are arranged in succession without distance in the direction of theair flow, wherein successive rows 36 each are displaced alternately toone side and the other side in the longitudinal direction of the ducts25 by half the width of the connecting bars or deflection points 38 andthus, as viewed in their direction of flow, axially. As indicated by thedashed line 40 in FIG. 8, the flow division forms zigzag flow paths forthe air flow through the flow chambers 26. The width of the fins 34,measured in the direction of flow, or their depth in this examplematches the height H1 of the fins 34, wherein the number of fin rows 36,measured in the direction of flow, is selected such that the depth ofthis exemplary embodiment of the cooler is 63 mm. The width of theconnecting bars 38, measured in the longitudinal direction of the ducts29, is selected such that the offset of the fins 34, denoted by P inFIG. 6, is 5 mm in this exemplary embodiment.

The arrangement of the fin rows 36, provided in the invention, and theirgeometric form having contact surfaces, formed via the connecting bars38, as deflection points on the boundary walls 24 permits a particularlyeffective heat coupling for heat transfer from the heated medium in theducts 25 to the fins 34, which have large surfaces against which airflows. In addition, because the fin rows 36 of each flow chamberexchange heat with both air-conveying ducts 26 and ducts 28, the coolersaccording to the invention provide a cooling capacity, which renders theuse of the coolers 18 for the dissipation of the heat loss occurringduring operation without supporting, motor-driven auxiliary fanspossible, while the mounting area on the nacelle 4 of a wind turbine canbe freely selected. This is without parallel in the prior art.

1. A cooler, having individual cooling elements (1) of stackedconstruction having ducts (25) extending in parallel to one another,each of which delimits a flow chamber (29) for the throughflow of aliquid medium to be cooled, between which at least two layers (3, 5) ofindividual rows (36) of meandering fins (34) extend, which for thethroughflow of air jointly delimit a further flow chamber (26, 28) each,characterized in that the respective one flow chamber (29), free ofobstacles, permits a laminar flow of the liquid medium through theassignable duct (25) in one throughflow direction, in that the height(H1) of each fin (34), viewed transversely to the direction ofthroughflow of the liquid medium, has at least the same height (H2) asthe free throughflow cross section of the flow chamber (29) of theadjacently arranged duct (25), viewed in parallel to the extension ofthe respective fin (34), and in that in every layer (3, 5), a pluralityof rows (36) of several fins (34) are arranged in succession, which eachviewed in the direction of throughflow of the duct (25) are offset (P)from each other.
 2. The cooler according to claim 1, characterized inthat at least part of the fins (34) of each layer (3, 5) adjoining oneanother extends in a bar-like manner each, forming a waveform betweentwo respective opposite deflection points (38), and in that deflectionpoints (38) of two adjacent layers (3, 5) are congruently facing eachother in a joint plane (E) adjoining the adjacently arranged ducts (25)of a cooling element (1).
 3. The cooler according to claim 1,characterized in that in the respective plane (E) a partition wall (27)extends in parallel to the throughflow direction of the liquid medium inthe ducts (25).
 4. The cooler according to claim 1, characterized inthat the respective partition wall (27) has the same material thicknessas the fins (34) forming the waveform.
 5. The cooler according to claim1, characterized in that the height (H1) of a single bar-like fin (34)is preferably three to six times, and particularly preferably fivetimes, the height (H2) of the flow chamber (29) for a duct (25).
 6. Thecooler according to claim 1, characterized in that the flow chamber (29)of every duct (25) has a free opening cross-section, which is solelydelimited in a rectangular shape by peripheral duct walls (23, 23′, 24),whose material thickness preferably matches the wall thickness of therespective fin (34).
 7. The cooler according to claim 1, characterizedin that the offset (P) is selected in such a way that the respective fin(34) of a further fin row (36), arranged between two to each otherparallel, offset-free fin rows (36), extends offset from the adjacentfins (34) of the two adjacent fin rows (36) by a predeterminable axialdistance, in parallel to the respective duct (25), viewed in its flowdirection.
 8. The cooler according to claim 1, characterized in that theoffset (P) is 3 mm to 8 mm, preferably 4 mm to 6 mm, particularlypreferably between 5 mm to 5.9 mm.
 9. The cooler according to claim 1,characterized in that the height (H1) of a single fin (34), viewedtransversely to the direction of flow through a duct (25), is between 5mm to 15 mm, preferably 12 mm, and in that the total depth of everycooler element (1), having a plurality of fin rows (36) arranged insuccession, is 60 mm to 90 mm, preferably 63 mm and 82 mm, in depth. 10.The cooler according to claim 1, characterized in that the wallthickness of the fins (34), formed from a sheet material, is 0.15 mm to0.4 mm, preferably 0.2 mm, and the wall thickness of a panel, consistingof sheet material, as a partition wall (27) between the fin rows (36) is0.2 mm to 0.8 mm, preferably 0.4 mm.
 11. The cooler according to claim1, characterized in that the meander shape of the respective fin row(36) has bar-like fins (34), extending in parallel to one another, andin that two adjacent fins (34) of the fin rows (36) are each integrallyinterconnected via the deflection points (38) in the form of connectingbars, which extend in parallel to the ducts (25) having the boundarywalls (24), in their direction of flow.
 12. The cooler according toclaim 1, characterized in that the fin rows (36) and the ducts (25)extend between two media-conveying main struts (20) forming the fluidconnections with the ducts (25) and span a rectangular front face (16)as cooler surface, and that 20 to 48, preferably 25 to 63, particularlypreferably 54 ducts (25) form the effective cooler surface.
 13. A windturbine, in which at least one cooler according to claim 1 is spatiallyassigned to a nacelle (4) of the turbine, for the purpose of flowthrough the flow chambers (26, 28) without any fan drive only based onthe blade air flow and/or purely wind-driven ambient air.